1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a lighting device and a method for controlling the same. More particularly, the present invention relates to a Light Emitting Diode (LED) lighting device capable of correcting a change of wavelength of light output from an LED element according to changes in temperature, and a method for controlling the same.
2. Description of the Related Art
The technology related to using solid semiconductor light sources, such as LEDs and Laser Diodes (LDs), for image display devices has been vigorously researched. In particular, an LED backlight device using an LED having three colors, such as red, green and blue (R, G, B), which can be used to represent a wide spectrum of colors, has become popular as a backlight device for LCD image display devices.
FIG. 1A is a block diagram illustrating the configuration of a conventional LED backlight device. As shown in FIG. 1A, the conventional LED backlight device comprises a pulse width modulation (PWM) generator 110, an LED driver 120 and an LED light source 130.
The PWM generator 110 generates PWM signals in duty ratios suitable for each of R, G and B LED arrays which constitute the LED light source 130, and inputs the PWM signals to R, G and B drivers respectively in the LED driver 120. The duty ratio indicates the ratio of a cycle of the PWM signal to the on time of the PWM signal. The LED driver 120 supplies electric current to the LED light source 130 according to the input PWM signal and, thus, emits light from the LED light source 130.
In order to improve the image quality and reduce power consumption, dimming the luminance of the LED backlight device is required. FIG. 1B is a view provided to describe representative LED luminance dimming methods, an analog dimming (A_dim) method and a PWM dimming (P_dim) method. As shown in FIG. 1B, an analog dimming method adjusts the luminance of the LED element by modifying the intensity (amplitude) of an electric current of a PWM pulse supplied to the LED element, and a PWM dimming method adjusts the average electric power supplied to the LED element by modifying the ratio of on-off of a PWM pulse.
Meanwhile, emission features such as the luminance and wavelength of the LED element in LED back light devices depend on changes in temperature. In order to correct the emission features caused by changes in temperature, a PWM dimming method can be used. A PWM dimming method, however, still has problems due to the change of the wavelength of the aforementioned light output from the LED element, because the change of the wavelength of the output light is not corrected.
Therefore, a light emitting device maintaining the desired chromaticity by correcting the change of the wavelength according to changes in the temperature is desired.